The present invention relates to a bearing structure for a drum pedal used for playing a drum such as a bass drum.
A drum pedal includes a base, a footboard, a shaft, a beater, and a chain belt. Force pressing down the footboard of a drum pedal is transmitted to the shaft through the chain belt, so that the beater is rotated with the shaft and strikes the drum. The drum pedal therefore includes a bearing structure having roller bearings or slide bearings that rotatably support the shaft. Known bearing structures for drum pedals include those disclosed in Patent Documents 1 and 2.
The bearing structure disclosed in U.S. Pat. No. 5,388,494 includes posts 80, one of which is shown in FIG. 9. A horizontal hole 80a extending along the axis of a shaft 81 is formed in an upper end of the post 80. A threaded hole 80b is formed in the upper end of the post 80. The threaded hole 80b extends perpendicularly to the axis of the shaft 81 and communicates with the horizontal hole 80a. An end of the shaft 81 is received in the horizontal hole 80a of the post 80, together with a ball bearing 82 and a collar 83.
According to the bearing structure disclosed in U.S. Pat. No. 6,504,088, a recess 90a having a semicircular cross section is formed in the upper end of each post 90 as shown in FIG. 10. In the upper portion of each post 90, threaded holes 90b are formed above and below the recess 90a. A cap 91 having a recess 91a is attached to the upper portion of each post 90. The recess 91a has a semicircular cross section. The recess 90a of each post 90 and the recess 91a of the associated cap 91 form a horizontal hole having a circular cross section. Each end of a shaft 93 is received by the horizontal holes with a pair of bearings 94 and a cylindrical barrel 95.
In the case of the bearing structure disclosed in U.S. Pat. No. 5,388,494, a screw 84 is threaded into the threaded hole 80b of the post 80, so that the distal end of the screw 84 is pressed against a circumferential surface 83a of the collar 83. This fixes the position of the ball bearing 82 in the axial direction. However, according to this method, in addition to the fact that the position of the ball bearing 82 is fixed by the collar 83, the screw 84 fixing the collar 83 is fastened to the threaded hole 80b in a direction different from the axial direction of the shaft 81 (from above in FIG. 9). In this case, the ball bearing 82 is not completely fixed to the post 80, and a small gap is likely to form between the ball bearing 82 and the post 80 as the drum pedal is operated. This may cause deviations in the rotational axis of the shaft 81 and thus create noise while the drum is being played.
In the case of the bearing structure disclosed in U.S. Pat. No. 6,504,088, the screws 96 are threaded to the threaded holes 90b to fix the caps 91 to the posts 90, thereby fixing the position of each bearing 94 in the axial direction. However, as in the structure disclosed in Patent Document 1, the screws 96 for fixing the caps 91 are fastened to the threaded holes 90b along a direction different from the axial direction of the shaft 93. Further, according to Patent Document 2, the fastening force of the screws 96 is likely to act on the bearings 94 along the radial direction of the bearings 94. This may hinder the movement of the balls in the bearings 94, and the pedal cannot be operated smoothly.